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Topic: laser security (Read 1275 times)

Hello i am trying to make a laser security system so far i have...photo resistorsled'sand a laser pointermy problem starts with the photo resistor i made the circuit and it worked but there was 1 problem i want the led to light up when the laser beam is broken but it this case its lighting up when its complete and turns off when its brokeni need it to turn on when its broken and off when its complet

thanks for reading note (please no "how to make a laser security system tutorials")

ok thank you for your postso (i just read the transiter tutorial) i take it that transiters can also be turned on with a lower than voltage for example "5v above transiter is off, below 5v transister is on"please tell me if i get it

Not sure which transistor tutorial you read (a link would be helpful so that I can read the exact same one).

If this is on Bi-polar transistor, NPN & PNP types, then these are turned on with current flow through the base and emitter. The voltage required is about 0.6V due to the emitter diode but it is the current that turns on a bi-polar transistor.

If the tutorial is on MOSFET transistor then a voltage applied to the gate turns on the MOSFET. For an N-channel the transistor turns on when the gate voltage is higher than the source. The threshold voltage is different on different MOSFETs therefore one needs to refer to the data sheet for the MOSFET being used. Many will turn on with the gate 5 Volts greater than the source but other may need as much as 10 Volts.

Either a Bi-polar or MOSFET transistor can be used to invert the LED drive. Which type did you read about?

what would the name off a item be that would take for example , if 5 volts were givin to a input it would stay offbut if it was below 5 it would turn on. if its on then it allows a seperet power source thou to a output

The SoR transistor tutorial is a very basic introduction and really does not give enough information on properly using any of transistor. Do additional search for detailed tutorial on transistor usage.

In my post above I listed the possible transistor types that could be used. These would be called:NPN Bi-polar transistorPNP Bi-polar transistorN-ch MOSFET transistorP-ch MOSFET transistorElectronics catalogs, google and the SoR tutorial page search function can use these names.

what would the name off a item be that would take for example , if 5 volts were givin to a input it would stay offbut if it was below 5 it would turn on. if its on then it allows a seperet power source thou to a output

A circuit

Like eg. this:

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Regards,Søren

A rather fast and fairly heavy robot with quite large wheels needs what? A lot of power?Please remember...Engineering is based on numbers - not adjectives